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Myocardial Perfusion Changes Following Optimal Medical Treatment in Symptomatic Hypertrophic Cardiomyopathy

Background: Microvascular dysfunction is a hallmark of hypertrophic obstructive cardiomyopathy (HOCM) and can be visualized non-invasively using cardiac magnetic resonance (CMR) perfusion imaging. In parallel, the six-minute walk test (6MWT) is an established clinical tool to assess submaximal exercise capacity in patients with structural heart disease. Despite its widespread use, the relationship between objective changes in myocardial perfusion and functional improvements assessed by the 6MWT remains insufficiently explored in patients with HOCM on optimal medical therapy (OMT). Aim:This study aims to evaluate whether changes in functional capacity, measured by the 6MWT, correlate with changes in myocardial perfusion reserve (MPR) in HOCM patients treated with OMT. Methods: We will include patients diagnosed with obstructive HCM who previously underwent clinically indicated CMR perfusion scans for risk stratification. These patients are regularly followed in the HCM outpatient clinic of the Medical University of Vienna, where standardized 6MWTs are performed in routine care. Approximately one year after the baseline CMR, a follow-up CMR will be conducted to assess changes in perfusion parameters. This second CMR is clinically justified for improved individual risk stratification as recommended by the 2023 ESC Guidelines on Cardiomyopathies. The primary objective is to assess the correlation between the change in the walking distance in the 6MWT and the change in MPR over a one-year interval. Secondary endpoints include changes in myocardial blood flow (MBF) at rest and during pharmacological stress. All assessments will be integrated with clinical, echocardiographic, and laboratory evaluations.